1. Field of the Invention
This invention relates to telephone subscriber loop testing systems and, more particularly, to universal testing arrangements for subscriber loop carrier systems.
2. Description of the Prior Art
It is known to provide a plurality of subscriber channels over a lesser plurality of metallic pairs by using conventional analog or digital carrier techniques. A typical analog carrier system is shown in the copending application of B. S. Bosik, Serial No. 974,384, filed Dec. 29, 1978, now U.S. Pat. No. 4,196,321, issued Apr. 1, 1980. A digital subscriber loop carrier system is shown in J. L. Caldwell U.S. Pat. No. 3,963,869, granted June 15, 1976.
Numerous techniques for testing the carrier portions of these carrier systems are also known, such as that disclosed in the aforementioned application of B. S. Bosik and as shown in J. E. Dail U.S. Pat. No. 4,002,847, granted Jan. 11, 1977. Such systems, however, involve not only carrier-derived channels but also voice frequency drop wires from a remote carrier terminal to the subscriber served thereby. It is desirable to test both the carrier-derived channel for a particular subscriber and the voice frequency drop for that subscriber, using a minimum amount of circuitry at the remote location. It is further desirable to accommodate these testing functions under manual or automatic control from testing facilites designed for use in testing metallic loops. With such an arrangement, special testing procedures are not required for such carrier-derived subscriber loops (as distinguished from subscribers served by metallic loops).